Over the last 40 years SJCRH has maintained a highly-productive and distinguished record in the development of new treatments of childhood cancers (Figure 1). The continued success of this ongoing effort is made possible by the conduct of innovative early phase clinical trials by collaborating clinical and laboratory research groups within the Cancer Center. Historically, these clinical trials have focused on the pharmacokinetic properties, clinical efficacy and toxicity of drugs, since most were believed to act through non-specific cytotoxic mechanisms. Recent advances in understanding of the biology of cancer have led to the development of drugs that target specific molecules within cancer cells, e.g. inhibitors of tyrosine kinases. Therefore, over the last 5 years the proportion of the clinical trials conducted within the Cancer Center that test molecular targeted therapies has increased to between 50 and 75% (Figure 1). The proper evaluation of the anticancer properties of this new class of drugs requires assessment of the expression and activity of the drug target within patient tissues alongside measures of drug pharmacokinetics, efficacy and toxicity. Therefore, to ensure that SJCRH remains at the forefront of anticancer drug development it has established the MCTC that provides: expert advice on the incorporation of molecular assays of drug target expression and activity within clinical trials;systems for the efficient and proper collection and handling of clinical samples;expert laboratory facilities for sensitive and specific analysis of drug targets in these clinical materials;and support for the appropriate analysis and interpretation of all data generated by these assays. In this manner the MCTC Shared Resource responds directly to recommendations made by the National Cancer Institute's (NCI) Clinical Trials Committee (response to the Clinical Trials Program Review Armitage Committee), and to section 7 of templates provided for both Phase I and II trial design by the Cancer Therapeutics Evaluation Program (CTEP) at NCI.